The subject invention relates generally to fluid filter media products and more specifically to fluid filter media products comprising a pleated fluid filter medium.
Fluid Filters are used in a variety of applications to remove particulates and debris (i.e., contaminants) from fluids. For example, fluid filters are commonly used in machinery (e.g., vehicles, engines, etc.) to filter oil, gas, air, and/or other fluids. For example, most vehicles (e.g., cars, trucks, tractors, etc.) contain an oil filter, gas filter, transmission filter, and air filter that remove contaminants from the oil, gas, transmission fluid, and air. Industrial equipment (e.g., compressors, hydraulics, vacuums, purifiers, etc.) often use fluid filters as well to remove contaminants and/or to purify fluids.
Fluid filters often include a filter medium that is placed in the fluid stream or fluid path so that the fluid is forced to flow through (i.e., pass through) the filter medium. The filter medium may be made of a porous or semi porous material that entraps and sequesters suspended contaminants as the fluid passes through the filter medium. The porosity and/or permeability of the filter medium may be varied depending on the application and/or the size of the particles/contaminant to be filtered. For example, in applications that require virtually contaminant free fluids, the filter medium may be constructed to filter very fine particles. In applications where filtering very fine particles is less of a concern, the filter medium may be constructed to only filter larger particles. Because the fluid is forced to flow/pass through the filter medium, a pressure drop normally exists across the filter medium. The pressure drop across the filter medium may depend on the size and/or type of particle/contaminant to be filtered, with finer particle/contaminant filtering resulting in an increased pressure drop.
The amount of fluid that can be filtered by a fluid filter in a given amount of time and pressure depends on several factors including the surface area of the filter medium. Generally, as the surface area of the filter medium increases, the more fluid the filter is able to filter in a given amount of time. Similarly, over time, the increase of the pressure drop across a filter medium is generally reduced as the surface area increases due to an increased ability to filter particles without becoming saturated. Thus, the lifespan of the fluid filter is also increased because the filter is able to filter more fluid before becoming saturated with filtered contaminants/particles and exceeding the pressure drop limits. However, the surface area of the filter medium is often limited by the volume that the fluid filter may occupy. To increase a filter medium's surface area for a given volume, the filter medium may be pleated by bending the filter medium back on itself several times.
A problem associated with pleating the filter medium is that adjacent pleats may collapse, or in other words, the surfaces of adjacent pleats may touch. Adjacent pleats may collapse due to the pressure drop across the filter medium and/or due to prolonged use. Pleat collapsing generally may increase over the life of the fluid filter due to pressure drop increases due to media loading. Pleat collapsing often restricts or eliminates fluid flow through the collapsed area of the filter medium, which may result in an additional increased pressure drop across the filter medium and/or in a failure of the fluid filter to properly filter a fluid (e.g., the fluid filter does not filter a sufficient amount of fluid in a given amount of time).
High performance (e.g., finer particle/contaminant filtering) and/or long life fluid filters often require greater filtration efficiency and higher dirt loading properties, which means that an increased number of pleats may be required when compared to similar lower quality filters. Such high quality filters may experience a greater risk of pleat collapsing due to the increased number of pleats and/or due to the reduced spacing between the pleats. In addition, high quality filters are often subjected to increased pressure drops due to finer particle filtration, which may further increase the risk of pleat collapsing.
To reduce the pleat collapsing problem, a separator may be applied between the pleats on either or both the upstream side and downstream side of the filter medium. The separator may be a thin strip or bead of glue applied between the pleats (e.g., hot melt glue beads), crimps in the filter medium, nylon mesh or screen applied to the filter medium, etc. The need for separators may increase as the risk of pleat collapsing increases. Adding separators to fluid filters, however, often increases the manufacturing time, manufacturing costs, and/or material costs of the fluid filter. Additionally, adding an extra layer to act as separators in the pleat configuration takes up media space, thus reducing the number of pleats in the filter or requiring an increase in the filter element size. In addition, pleat collapsing may still occur despite the use of a pleat separator.